Tap changer



z. 0. 5T. PALLEY 5,303

T A P CHANGER Sept. 8, 1942.

Filed April 3, 1942 Invehtor:

Zcfl'ban 0.3%. PaHey,

y His Attorney.

Patented Sept. 8, 1942 Zoltan 0. St.

General Electric New York Application April 3, 1942, Serial Pailey, Plttsfl eld, Mala, aslignor to Comm-n1. a corporation of 3 Claims. (01. 111-119) This invention relates to tap changers and more particularly to an improved arrangement for changing taps in a load circuit without interrupting the load current. 1

Many electrical devices, such as transformers, reactors, potentiometers, rheostats and Petersen coils, are often provided witha plurality of taps to which it is desired to make selective electrical connection without interrupting the current through the device. In accordance with the present invention there is provided a novel and simple arrangement of this type which makes use of the tap-to-tap voltage diflerence for energizing an electromotive device which thereupon automatically completes a tap change in a very rapid and very reliable manner.

An object of the invention is to provide a new and improved tap-changing arrangement. I

Another object of the invention is to provide an improved arrangement for changing taps in electrical apparatus without interrupting the load current of the apparatus.

The invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing Fig. 1 is a circuit diagram in which a plan view is shown of my novel tapchanging means and Fig. 2 shows a side. elevation of the tap-changing means.

Referring now to the drawing, there is shown therein by way of example a transformer winding I provided with a plurality of taps 2 terminating respectively in fixed tap contacts. The winding i may be any one of a number of insulated windings of a conventional transformer or it may be an autotransformer. Load current may be considered as entering the winding through a conductor 3 and leaving it through a conductor 4 although,

of course, the direction of current flow is immaterial. As shown more clearly in Fig. 2, the fixed tap contacts which are connected to each of the taps 2 are double contacts 5 and I which co operate respectively with movable contacts I and I. These two movable contacts normally engage fixed tap contacts which are connected to the same tap and the circuit conductor l is connected directly to the movable contact 8 so that normally substantially all of the load cur-rent flows through the movable contact 8. This contact is a trailing or follow-up contact with respect to the contact I which is a leading contact in so far as the operatoin of the invention is concerned. Thus, contact I is connected to main driving means 9 !or the tap-chs s fl means.

iii

For causing automatic follow-up operation of the trailing contact 0 there is provided an electromotive means of any suitable type, shown, for example, as a solenoid electromagnet III carried by the leading contact I and having its plunger connectcd by a pivoted link I I to the trailing contact I which in turn is 'pivotally mounted at I! on the leading contact I. This magnet is connected electrically between the two movable contacts.

For controlling the electrical characteristics of the tap-changing circuit suitable impedance means l3 may be connected in circuit with the electromagnet ID, if desired, and this impedance means may be 01' any type, such as a resistor, reactor, capacitor, or any suitable combination thereof.

The operation of the illustrated embodiment of the invention is as follows: Assume that inFig. 1 the movable contact I had previously been making connection to the same tap with which thetrailing contact 8 is shown as making connection and that, therefore, the leading contact I has just been moved in a counterclockwise direction to the next lowermost tap. During this movement the transformer load current is substantially unaffected lbecause substantially all of it flows through the movable trailing contact 8 as the impedance through the current path of this contact is lower than the impedance through the contact I because 0:15 the impedance of the device Ill and also of the device l3, if it is present, which is in series with the latter. However, as soon as the leading contact 1 engages the next adjacent tap contact the tap-to-tap voltage difference will be impressed across electromagnet l0, thereby causing it to attract its plunger whereby force is applied to the trailing contact 8 tending to snap it rapidly in the follow-up directioninto alignment with the leading contact 1. Ordinarily, there will be a momentary are drawn when the trailing contact 8 leaves its tap contact but this are will not be carried across between fixed or tap contacts and when it goes out during the motion of the trailing contact all of the load current will be transferred to'the leading contact I and will iiow through the magnet III and through the impedance It, if present. There is, therefore, ample operating current for the electromagnet for in- I follow-up operation of the contact it is completed the surlng that the i is completed. As soon as magnet l0 and impedance l3 cuited and all 0! the current will be returned to the trailing contact 8.

It will be obvious from the above that the same operation or results would follow ii the will be short cirleading contact had been moved clockwise instead of counterclockwise and that no matter how the leading contact I is moved, as soon as it ages an adjacent contact the electromagceans is automatically energized and proa powerful reliable force for causing up motion oi the contact 8 whereby the contact will be aligned with the former contact.

illethere has been shown and described a .cular en codiment of this invention, it will be obvious to those skilled in the art that various change and modifications can be made therein without dc ing from the invention and, therefore, it is an d in the appended claims to cover 2113 such chan es and modifications as fall within the true spirit and scope of the invention.

What i. claim as new and desire to secure by Letters Patent oi the United States is:

i. In combination, an electrical load current I carrying device provided with a plurality of taps, and switching means for tra sfer S i 108d current from tap to tap without interrupting said current comprising a leading movable contact and a trailing movable contact which normally make connection to the same one of said taps and through the trailing one 01' which substantially all of said load current normally passes, means for moving the leading one of said contacts in either direction to an adjacent tap, and electromotive means responsive to the tap voltage difference applied between said movable contacts when said leading contact reaches said adjacent tap for moving said trailing contact in a follow-up direction into connection with the tap to which said leading contact has been moved.

2. In combination, a transformer winding provided with a plurality of tape which are spaced substantially equally electrically, a pair 01' movable contacts for normally making connection to the same tap, one or said contacts being a trailing contact and being connected normally to carry substantially all 01' the transformer load current, the other of said contacts being I. leading contact, means for moving said leading oontact to an adjacent tap, and means including an electromagnetic means connected between said contacts for causing follow-up motion of said trailing contact when said leading contact reaches an adjacent tap and thereby causes the tap-to-tap voltage difference to be applied to said electromagnetic means, said electromagnetic means being capable of carrying the transformer load current during at least a part of the follow-up movement 01 said trailing contact.

3. In combination, a transformer winding provided with a plurality of tape which are spaced substantially equally electrically, a pair of movable contacts for normally making connection to the same tap, one of said contacts being a trailing contact and being connected normally to carry substantially all or the transformer load current, the other or said contacts being a leading contact, means for moving said leading contact to an adjacent tap, means including electromagnetic means connected between said contacts for causing follow-up motion 01 said trailing contact when said leading contact reaches an adjacent tap and thereby causes the tap-totap voltage difference to be applied to said electromagnetic means, said electromagnet being capable 01' carrying the transformer load current during at least a. part 01' the follow-up movement of said trailing contact, and impedance means connected in circuit with said electromagnetic means for controlling the volt-ampere characteristics of the circuit during a. tap changing operation.

ZOLTAN 0. ST. PALLEY. 

